Amputees have retained prosthetic devices on their residual limbs using various vacuum or suction arrangements for many years, particularly since the advent of soft cushion liners that are worn between the residual limb and the prosthetic socket. Typically, a one-way valve is provided at a distal end of an otherwise closed socket that is arranged to receive the distal end portion of a residual limb whereby air in front of the distal end of the residual limb may be exhausted through the one-way valve until the residual limb and a corresponding liner are fully inserted into the socket.
The one-way valve thereafter is maintained in a closed condition and forces tending to separate the prosthetic socket from the residual limb are resisted by induced sub-atmospheric pressure between the distal end of the residual limb and the distal end of the socket.
It is necessary, of course, with vacuum suspensions to maintain the sub-atmospheric pressure or vacuum at the distal end of the socket. Thus, appropriate sealing sleeves and other arrangements are typically provided to prevent influx of air around the distal end of the residual limb and into the distal end of the socket. Obviously, with a vacuum suspension system, any significant loss of vacuum will result in separation of the prosthetic socket from the residual limb unless an additional element is provided to retain the socket attached to the residual limb.
It has been recognized in the prior art to provide a vacuum reservoir chamber maintained at sub-atmospheric pressure and in communication with a prosthetic socket for the purpose of maintaining an appropriate partial vacuum within the socket in order to compensate for variations in volume of the residual limb while the prosthetic socket is worn and to compensate for air leakage around the residual limb. An integral system having vacuum pressure sensors and evacuation means is carried by the prosthetic socket, or by an extension of the prosthetic socket.
U.S. published patent application No. 2004/0260403-A1, published on Dec. 23, 2004, herein incorporated by reference and co-owned by the assignee of this disclosure, provides a self-contained vacuum chamber socket system without the additional system to maintain the vacuum within the chamber. This configuration is an improvement over a vacuum chamber socket system that includes the additional weight of vacuum pressure sensors and evacuation means. However, the unavoidable leakage of air into the socket can raise the pressure within the vacuum chamber. Once the pressure within the vacuum chamber rises to atmospheric pressure, the residuum may slide within the socket. This is due to the expandability and compressibility of the air that is within the vacuum chamber.
Thus, while it is known to use suction to maintain a residual limb within a socket, it is desirous to provide a suitable arrangement that does not require an integral system of pressure sensors and an evacuation means for maintaining a sub-atmospheric pressure between the residual limb and the inner walls of a socket despite variations in volume of the residual limb and further despite minor air leakage around the residual limb tending to relieve the vacuum within the socket.